[linh nguyen]

Hi,

I am Linh. I quite new with using UDF. I was writing this UDF using CD_MOTION Macro.

My objective is solve the amplitude of motion for single degree of freedom using Finite different method. But I have two errors:
- syntax error : missing ';' before 'type'
- subscript is not of integral type.

Here is my UDF code.

#include "udf.h"
#include "stdio.h"
#include "stdlib.h"
#include "math.h"
#include "dynamesh_tools.h"
#include "storage.h"
static real v_prev = 0.0;

FILE *fout;

DEFINE_CG_MOTION(cylinder, dt, vel, omega, time, dtime)
{
Thread *t;
Domain *d = Get_Domain(1);
face_t f;
real NV_VEC (A);
real force;
real mass = 1.443;
real wn = 0.183;
real k = mass*wn*wn;
real c = 2*mass*wn*0.0072;

/* reset velocities */
NV_S (vel, =, 0.0);
NV_S (omega, =, 0.0);

if (!Data_Valid_P ())
return;

/* get the thread pointer for which this motion is defined */
t = DT_THREAD(dt);

/* compute pressure force on body by looping through all faces */
force = 0.0;

begin_f_loop (f, t)
{
F_AREA (A, f, t);
force += F_P (f, t) * NV_MAG (A);
}
end_f_loop (f, t)

/* compute pressure amplitude of motion by Finite Different Method*/

NMAX = int(time/dtime) + 1;
real X[NMAX];
for(int i = 0; i < NMAX; i++){

X[0] = 0;
X[1] = 0;
X[i+1] = (force - X[i-1]*(mass/(dtime*dtime) - c/(2*dtime)) - X[i]*(-2*mass/(dtime*dtime) + k))/(mass/(dtime*dtime) + c/(2*dtime));
X[i+1]=DT_CG(dt)[1]; /*Assign to updated */

Message ("time = %f, force = %f, displacement = %f\n", time, force, X[i+1]);
fout = fopen("results.txt", "a");
fprintf(fout, "%f %f %f\n", time, force, X[i+1]);
fclose(fout);
}
}


Thanks for your help

Linh